The phase of matter can be changed by:
2 answers:
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The question is incomplete, here is the complete question:
The decay constant for 14-C is In 1947, the famous cave paintings in Lascaux, France were discovered and testing revealed that charcoal in the cave contained 20% of the 14-C found in living trees. Write a formula for the age of the charcoal (hence of the associated paintings). Show your work to find this formula.
<u>Answer:</u> The formula for the age of the charcoal is
<u>Explanation:</u>
Carbon-14 isotope is a radioisotope and its decay process follows first order kinetics.
Rate law expression for first order kinetics is given by the equation:
where,
k = rate constant =
t = time taken for decay process = ? yr
= initial amount of the sample = 100 grams
[A] = amount left after decay process = (100 - 20) = 80 grams
Putting values in above equation, we get:
Hence, the formula for the age of the charcoal is
Answer:
Mass of aluminium in sample = 3.591 g ≅ 3.6 grams
Explanation:
Given that, A sample of aluminum absorbs 50.1 J of heat, upon which the temperature of the sample increases from 20.0°C to 35.5°C.
the specific heat of aluminum is 0.900 J/g- °C
The relation between heat absorbed and change in temperature is given by, Q = msΔT.
where Q = heat absorbed
m = mass of the substance
s = specific heat of substance
ΔT = change in temperature
Now, in our case, Q = 50.1 J ; s = 0.900 J/g- °C; ΔT= 35.5-20 = 15.5°C
⇒ m =
⇒ m = = 3.591 g ≅ 3.6 g
⇒ m ≅ 3.6 g